In the development of the Navy Pointer Tracker involving the beam pointing system for the Navy ARPA laser, it was required that an integrated source/sensor designated input beam alignment sensor (IBAS) be designed and utilized in the laser tracking system. It was the function of the input beam alignment sensor to maintain the angular and translational alignment of the optical path between the laser and the beam pointer. The servo loop consists of this IBAS, two double axis steering mechanisms, the servo electronics and a passive reference unit on the laser.
The IBAS looks back approximately ten (10) meters from its position on the optical bench of the Navy Pointer Tracker toward the laser with the help of its own visible He Ne laser which is the source. This He Ne beam runs parallel with the laser beam and is reflected from a mirror fastened to the laser. The returning beam re-enters the IBAS on the same optical center line at the outgoing beam. Within the IBAS housing, the returning beam deviates and splits into two paths. One path leads to the angle sensing detector, the other beam to the translation sensing detector. The resulting electrical signals are used to control the steering mirrors and with their help keep the laser beam on the optical path. Any optical apparatus must be optically aligned after assembly due to manufacturing tolerances on all machined mechanical parts as well as optical elements. The course alignment of the optical elements is achieved by the mechanical holding devices. In the case of the IBAS, the end of the optical paths are the two detector elements which, after focusing in their optical axis, needed a full in plane, two degree of freedom translation to bring the center of the detective surfaces accurately into the center of their appropriate laser beam. In another application, the optical element could be a reticle moved relative to the beam, or to the before undetermined pick-sensitive area of a detective element. A common apparatus used in the prior art is two orthogonal sliding elements stacked together supporting the part to be aligned. On IBAS, height was a problem as well as manipulation of the multiple slides at 90.degree. to each other. Access was from one side only. To move one sliding part A in a Y-axis motion is simple with the help of a screw pushing the slide along the Y axis. For O-backlash reasons, it may be necessary to force the slide back to the screw with a spring, so that a push-pull action can be produced. To move the slide in the X-axis, for instance, 90.degree. to the Y-axis and operated from the same side as the Y-axis is manipulated, one could shift the slide with the help of a 90.degree. knee lever, but the slide would need another orthogonal face to slide along, or instability would result.
The instant invention solves these problems and provides new and unexpected results.